Investigators did not visit the accident site because witnesses provided enough information to be able to determine the nature of the accident. Weather information from Sioux Lookout helped to confirm the kind of weather that the pilot encountered. The remoteness of the site made ground access difficult; however, the site was overflown by investigators and examined from the air. Photographs taken by Ministry of Natural Resources employees were reviewed to complement witness reports. Consequently, this analysis will not include the discussion of technical issues other than carburettor icing. When deteriorating weather conditions were encountered in the vicinity of Ignace, the pilot attempted to look for better weather by staying at low altitude and looking for a clear horizon beneath the cloud base. Because the pilot did not fully understand how the other aircraft had diverted around the marginal weather area, the pilot was expecting to find better weather ahead. Influenced by the perception that another pilot was in better weather on a different over-water route, the occurrence pilot flew across a land area towards the over-water route. However, the weather conditions rapidly deteriorated and the horizon disappeared in heavy rain. There was then no option of landing on a suitable lake and waiting out the weather. The chart in the AIP indicates that in heavy rain at the ambient temperature/dew point existing at the time of the accident, a risk of serious carburettor icing is present at any power setting. The fuel mixture of 100 low-lead aviation gasoline and MOGAS significantly increased this risk. Consequently, the engines' near simultaneous partial power loss was probably caused by carburettor ice, as reported by the pilot. The pilot's technique for the application of carburettor heat differed from the recommended company procedure; the pilot did not apply carburettor heat as a precautionary measure prior to entering the area of marginal weather. When the heavy rain was encountered, the pilot then had to contend with the increased workload of restoring engine power and flying in the rain at low level with no horizon, until power could be restored. When the pilot did apply carburettor heat, there was not sufficient time to clear the carburettor ice and restore engine power before contact with the trees. It is possible that the refraction effect of the rain on the windscreen led the pilot to believe that the aircraft was higher than it actually was and consequently, the pilot flew at an altitude that left no margin for dealing with emergency situations. The mounting of the first aid kit prevented the pilot from removing it quickly from the aircraft when the survivors abandoned the aircraft. The location of the survival kit behind the baggage prevented the survivors from removing the kit when exiting the aircraft and the kit was destroyed in the post crash fire.Analysis Investigators did not visit the accident site because witnesses provided enough information to be able to determine the nature of the accident. Weather information from Sioux Lookout helped to confirm the kind of weather that the pilot encountered. The remoteness of the site made ground access difficult; however, the site was overflown by investigators and examined from the air. Photographs taken by Ministry of Natural Resources employees were reviewed to complement witness reports. Consequently, this analysis will not include the discussion of technical issues other than carburettor icing. When deteriorating weather conditions were encountered in the vicinity of Ignace, the pilot attempted to look for better weather by staying at low altitude and looking for a clear horizon beneath the cloud base. Because the pilot did not fully understand how the other aircraft had diverted around the marginal weather area, the pilot was expecting to find better weather ahead. Influenced by the perception that another pilot was in better weather on a different over-water route, the occurrence pilot flew across a land area towards the over-water route. However, the weather conditions rapidly deteriorated and the horizon disappeared in heavy rain. There was then no option of landing on a suitable lake and waiting out the weather. The chart in the AIP indicates that in heavy rain at the ambient temperature/dew point existing at the time of the accident, a risk of serious carburettor icing is present at any power setting. The fuel mixture of 100 low-lead aviation gasoline and MOGAS significantly increased this risk. Consequently, the engines' near simultaneous partial power loss was probably caused by carburettor ice, as reported by the pilot. The pilot's technique for the application of carburettor heat differed from the recommended company procedure; the pilot did not apply carburettor heat as a precautionary measure prior to entering the area of marginal weather. When the heavy rain was encountered, the pilot then had to contend with the increased workload of restoring engine power and flying in the rain at low level with no horizon, until power could be restored. When the pilot did apply carburettor heat, there was not sufficient time to clear the carburettor ice and restore engine power before contact with the trees. It is possible that the refraction effect of the rain on the windscreen led the pilot to believe that the aircraft was higher than it actually was and consequently, the pilot flew at an altitude that left no margin for dealing with emergency situations. The mounting of the first aid kit prevented the pilot from removing it quickly from the aircraft when the survivors abandoned the aircraft. The location of the survival kit behind the baggage prevented the survivors from removing the kit when exiting the aircraft and the kit was destroyed in the post crash fire. Records indicate that the pilot was certified and qualified for the flight. While on a VFR flight, the pilot continued flight into adverse weather and lost all reference to the horizon. The pilot had been exchanging weather and position information with another company pilot and believed that the weather conditions would improve. The pilot deviated from the company practice of either staying on an over-water route or landing and waiting out the weather. The pilot may have been at a lower level than anticipated because of the refraction effect of rain on the windshield. The temperature and dew point at the time of the accident were conducive to serious carburettor icing at any power setting. The aircraft fuel mixture consisted of aviation gasoline and MOGAS and hence was more susceptible to carburettor icing than aviation fuel alone. The pilot's technique in attempting to eliminate carburettor ice was not as recommended by the company. The engines lost partial power, likely because of carburettor ice. There was insufficient time to recover from the partial power loss effects of carburettor icing. The location of the first aid and survival equipment prevented their quick removal during the rapid egress from the aircraft.Findings Records indicate that the pilot was certified and qualified for the flight. While on a VFR flight, the pilot continued flight into adverse weather and lost all reference to the horizon. The pilot had been exchanging weather and position information with another company pilot and believed that the weather conditions would improve. The pilot deviated from the company practice of either staying on an over-water route or landing and waiting out the weather. The pilot may have been at a lower level than anticipated because of the refraction effect of rain on the windshield. The temperature and dew point at the time of the accident were conducive to serious carburettor icing at any power setting. The aircraft fuel mixture consisted of aviation gasoline and MOGAS and hence was more susceptible to carburettor icing than aviation fuel alone. The pilot's technique in attempting to eliminate carburettor ice was not as recommended by the company. The engines lost partial power, likely because of carburettor ice. There was insufficient time to recover from the partial power loss effects of carburettor icing. The location of the first aid and survival equipment prevented their quick removal during the rapid egress from the aircraft. The pilot continued the flight into adverse weather at low level and force-landed the aircraft into trees when the engines experienced a partial power loss that was probably caused by carburettor icing.Causes and Contributing Factors The pilot continued the flight into adverse weather at low level and force-landed the aircraft into trees when the engines experienced a partial power loss that was probably caused by carburettor icing.